1. Field of the Invention
The present invention relates to a mechanism arranged in an image forming apparatus for conveying a paper sheet or similar recording medium and an image forming apparatus using the same.
2. Description of the Background Art
A copier, facsimile apparatus, printer or similar image forming apparatus includes a mechanism for conveying a paper sheet or similar recording medium with a pair of rotary bodies. The rotary bodies rotate in contact with each other to thereby nip the paper sheet therebetween. The paper sheet sometimes jams a sheet path arranged in the mechanism. In light of this, the mechanism should preferably be so arranged as to facilitate the removal of the jamming sheet. There has been proposed an image forming apparatus in which two rotary bodies rotatable in contact with each other are respectively mounted on the apparatus body and an openable cover mounted on the apparatus body. This type of apparatus allows the operator of the apparatus to easily remove a jamming sheet by opening the cover and thereby moving the rotary body mounted thereon away from the other rotary body.
The prerequisite with the two rotary bodies is that their axes of rotation be accurately parallel to each other; otherwise, the mechanism is apt to fail to convey a paper sheet straight and often brings about a jam. However, parallelism between the two rotary bodies is difficult to achieve because not only the position of the rotary body on the cover but also the position of the cover relative to the apparatus body and opening and closing operations thereof need certain accuracy. Moreover, even if parallelism is set up between the rotary bodies, the relative position of the rotary bodies varies when the door becomes unstable due to repeated opening and closing. It is therefore extremely difficult to maintain the rotary bodies parallel over a long period of time.
To prevent the cover from becoming unstable, a mechanism for opening and closing the cover may be formed of a highly rigid material or use may be made of a mechanism for preventing screws from being loosened. This kind of scheme, however, increases the cost of the apparatus.
Technologies relating to the present invention are disclosed in, e.g., Japanese Patent Laid-Open Publication Nos. 6-156798 and 2000-214718.
It is an objet of the present invention to provide a recording medium conveying mechanism capable of ensuring parallelism between two rotary bodies over a long period of time without resorting to any special measure against the instability of an openable cover, and an image forming apparatus using the same.
In accordance with the present invention, in a recording medium conveying mechanism for an image forming apparatus, a first and a second rotary body rotate in contact with each other for conveying a paper sheet to which a toner image is to be transferred. The first and second rotary bodies are respectively mounted on the apparatus body and an openable cover mounted on the apparatus body. The second rotary body moves into or out of contact with the first rotary body in interlocked relation to the closing or the opening, respectively, of the cover. The conveying mechanism includes a first support member rotatably supporting the first rotary body on the apparatus body and including a first engaging portion. A second support member rotatably supports the second rotary body on the cover and includes a second engaging portion. The first and second engaging portions mate with each other when the cover is closed.
An image forming apparatus including the above mechanism is also disclosed.